Questions tagged [speed-of-light]
The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.
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Can gravitational waves be compared with a sinking water phenomena?
Let say we have some water in the sink and open the closure.. The water starts to move towards it in a whirpool like manner.. If we have a table tennis ball and leave it near the hole of the sink it ...
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How can light have a speed when it devies what speed is?
For us to measure any movement, the "something" has to have a different position to some reference frame. now speed is defined by the amount of changed position( which we can tell by the ...
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What's the speed limit for things with mass?
So the speed limit of the universe is 299 792 458 m/s, but only massless things like photons can archieve this speed. Since things that have mass can reach 99.99999...% speed of light, does that mean ...
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How can Electricity travel at the speed of light?
If electricity is the flow of electrons, how come it can flow at the speed of light? Shouldn't how fast it moves be limited to a speed lower than the speed of light because it has mass?
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Relativistic Velocity-addition formula adds a scalar to a vector?
Sorry if this is a stupid question.
The formula for relativistic Velocity-addition is
$u = (v + u') / (1 + (vu'/c^2))$
It seems that v, v', u, and u' are vectors, while c is a scalar.
But 1 seems to ...
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Will we ever reach a speed even close to 75% the speed of light. If yes what physics are behind it? [closed]
Is it possible for human technology to get close to the speed of light. If yes, how long will it be before we reach that. And what formulas will work well for it.
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Measuring one-way speed of light [duplicate]
Veritasium's video explains why we can't measure the one-way speed of light: https://youtu.be/pTn6Ewhb27k?si=60Q0AffVdt09lJSb
However, I still don't completely get why this is the case.
Let's say that ...
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What would happen if the aether did exist and there was no such thing as relativity? [closed]
I'm curious as to the purpose of relativity and why the universe would function this way as opposed to a universe with an aether. So what would be different if we had an aether?
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What's wrong with this One-Way Speed of Light experiment? [duplicate]
I can't tell what's wrong with it.
Imagine the wheels of a car, jack the car, put a sensor on one wheel, a laser on another, start rotating, with enough speed the sensor will start to detect the laser ...
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How to explain light traveling two distances in the same frame of reference? [closed]
Suppose I have a "moving" frame of reference where I send a light beam from point A to two equidistant points B and C (equidistant in the moving frame of reference). From a "stationary&...
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Relativistic Effects on Electromagnetic Wave Propagation
So for a recent lab I had to calculate the length of a conductor by measuring the time it took a signal to reflect off of the open end. I used the very simple principle of $v=st$ and, knowing that the ...
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All Michelson-Morley experiments have only been done in non-inertial conditions. Does special relativity apply or not?
As far as I know not a single Michelson-Morley experiment has been done in non-inertial conditions. Shouldn't it be general relativity that applies to Michelson-Morley experiments done so far?
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Did the distances of the reflecting mirrors in Michelson Morley need to be precise to 100 nm or less?
When I took Physics, both in HS and College I was taught that the reason the Michelson Morley experiment "could" produce an interference pattern at the detector location was that the two ...
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Explain Time dilation for me with many easy to comprehend examples and reasons [closed]
I can’t wrap my head around this.
So didn’t Einstein came to believe time stops because he imagined watching a clock tower as he raced away in a near light speed train? He would then notice that the ...
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Calculating an arbitrary metric tensor (field) in vacuum: Make use of the constant speed of light?
The metric (=field of metric tensors) is the solution of Einstein's field equations when a special distribution of matter is given. It is among the unsolved problems of physics to calculate the metric ...
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How do i calculate change of momentum when I send a photon in the direction of travel
Say a spaceship is traveling at a certain velocity v (>>c) and it emits light from the nose of my spaceship in the direction of travel. The speed of light is finite and hence there should be a ...
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Reaching 50% the speed of light using a centrifuge
I've seen ideas and previously asked questions for reaching the speed of light through a long bar rotating at some high RPM for the tip to reach $c$. However it seems impossible, so I'm concerned is ...
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Clarification about the one-way vs two-way speed of light
I've just watched Why No One Has Measured The Speed Of Light by Veritasium, but I haven't really understood why this debate exists.
The reason for my misunderstanding, I believe, is that the whole ...
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Is it possible to detect your speed relative to light? [duplicate]
Let’s take two cases: (1) your velocity is constant and (2) you are accelerating.
(1) isn’t the answer no, like that’s a core idea of Einstein’s relativity stuff?
(2) I don’t know.
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How long does it take before neutrino velocities in the neutrino background radiation are substantially less than the speed of light?
The energy of photons is reduced by the expansion of space. Since the photons have been decoupled from matter their wavelengths have decreased from the visible range to the radio range.
The same ...
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Has the light postulated at the base of relativity ever been empirically validated? [duplicate]
How has the speed of light postulate in special relativity been empirically validated to establish it as a fundamental truth of physics? Considering historical experiments like the Michelson-Morley ...
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Speed of light postulate in special relativity in inertial vs. non-inertial frames
I'm trying to learn special relativity by myself. I've been following this series of videos, plus some other articles I've managed to find online. At this point I'm already quite far into the theory, ...
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Relativity of Simultaneity - Why doesn't the train/lightning example contradict the absolute speed of light?
I know similar questions have been asked here before, but none of them seem quite to address my particular confusion.
I'm not afraid of math (I did well in calc III last semester, for example) but my ...
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Does energy move as fast as light, just like photons?
I've been thinking about energy and how it travels, especially compared to photons. We all know that photons move around at the speed of light in a vacuum.
So, here's my question: Does this idea apply ...
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Newton-Cartan from GR
How does EFE reduce to Newton-Cartan Field Equation $R_{tt}=4\pi G \rho$ in Newtonian Limit? I understand its direct derivation from geodesics in weak field, what I am curious about is how EFE reduces ...
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Does current develops instantaneously as we apply potential difference?
I had this doubt from the starting since I studied current electricity, that if we apply a potential diff. Across a resistor, does the current flow instantaneously, if it does then the communication ...
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Time dilation query [closed]
In the light clocks, time ticks via the motion of light and since speed of light is constant therefore when the clock is in motion ,the photon has to cover a greater distance by the perspective of an ...
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When was it possible to observe the special-relativistic modification of Energy?
I am preparing a lecture for high-school students, and was wondering when it would have been possible to observe the special-relativistic modification of the Energy-velocity relation.
In more detail, ...
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Speed of light getting lower in densed medium [duplicate]
In densed medium speed of the light gets lower so in this kind of situation is there anything which can travel quicker than light?
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Apparent violation of laws of reflection for an inertial observer [duplicate]
I am actually having an introductory course in Special Relativity in which I was looking at the Michelson Morley experiment. And I have this silly confusion.
The setup for the Michelson Morley ...
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What could a year long journey look like, while traveling near the speed of light, through the lens of that telescope?
Hypothetically speaking if you had a satellite going near the speed of light in a straight line towards an exoplanet light years away and that satellite had a telescope pointed at the surface of an ...
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If mass was to reach the speed of light it becomes infinitely heavy. Does this mean it has become a black hole singularly? [duplicate]
If mass reaches the speed of light, it becomes infinitely heavy. Does this mean that it has become a black hole singularly?
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If you had a ridiculously bright laser, and you were positioned at a point far enough away, could you see the light move through space?
Just a question out of pure curiosity that I can't seem to find an existing answer to. Let's say you are at an empty point in space, and your friend has the universes strongest and brightest laser 10 ...
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Any experiment for relative simultaneity?
Any introduction of relative simultaneity usually is like this :
Alice on a train car shines two beams of light towards both ends where two clock are. She sees both clocks see the light at the same ...
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Foucault's measurements of the speed of light
I understand that you can — in principle — measure the speed of light with the rotating mirror experiment.
What I don't understand: How can you accurately measure (or fix) the number of rotations of ...
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Relativity on a massive bridge
Suppose there is a ridiculously large bridge, fixed at either end (light seconds long at least). The bridge is constantly under the influence of gravity. If the ends are severed simultaneously, the ...
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How would we perceive light arriving to us from a distance source?
Imagine being in space 5 light minutes from the source of a beam of light. The source of the beam of light is initially switched off.
The light is turned on. When it is turned on you would see ...
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Is it possible for photons to gain mass and interact with the higgs field? [closed]
If objects gain mass as they approach the speed of light, is it possible that as a photon "attempts" to exceed the speed of light it gains enough mass to interact with the higgs field ...
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Speed of wave more than $c$
We are always told that information cannot travel faster than light (speed $c$). So, my question is, if we talk about a wave lets say a transverse wave. We can define a wave as the systematic ...
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Why does the assumption that speed of light $c$ is constant exist? [closed]
This is I'm sure a very basic and juvenile question. Why do we take the assumption that $c$ is constant in all situations to be a law? It does work out that it fits the standard model well but it has ...
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Black Holes and Gravity [duplicate]
We know that nothing including light can escape the gravitational pull of black hole. Now special relativity says that nothing travels faster than speed of light. Then how can effects of gravity due ...
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Is there a *geometric* explanation for why photons have no rest frame?
I've read the various threads on this site that talk about it being impossible for photons (or massless particles in general, really) to have a rest frame, and the answers all seem to boil down to &...
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Can gravity make something faster than light? [duplicate]
Scenario,
Let's say we have complete vacuum and nothing in the universe.
If we place 2 bodies at infinite separation and have HUGE masses ($m1, m2 \sim 10^{1000}$ kg or something):
They will attract.
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Relativity of bodies in motion in space
I have learnt that if we are travelling in space we have no way to tell if we are moving towards something or if it is the something that is moving towards us; to either object they judge that they ...
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How do we know that the speed of light is constant everywhere, not just here? [duplicate]
It might well be that universal constants, say the speed of light, are only constant as far as we can tell in our chunk of the universe - in the same way that the Earth looks flat in the area you live....
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Why does speed of light relate to the density of the surrounding medium?
Why does the speed of light relate to the refractive index of its surrounding medium while it is a massless electromagnetic wave?
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The value of speed of light in different regions of spacetime
This question of mine started shaping in my head first while I was looking for the most fundamental answer for the speed of light's value and its property of being the limit.
I have convinced myself ...
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Speed of light affected by gravity or frame dragging effect
If we do not really 100% know how light works as a oscillation we also do not know is its speed indeed constant no matter is there a space or space-time motion that can affect it. Could a device that ...
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Speed of Light and Time [closed]
I'm an amateur and this is my first question here, I'm trying to formulate question about a general representation I have in mind after trying to grasp the idea of relativity and the concept of space-...
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What changes do we have when we consider time dilation of light clock? [closed]
According to the special theory of relativity, in moving body all physical processes are slower than they should be for a stationary body according to the time counts of a fixed (laboratory) frame of ...
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